Person:
Misch,
Jacob
Misch,
Jacob
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ORCID
0000-0002-8986-6497
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ItemDataset for "Investigating shock and vibration exposure of a manual wheelchair during multi-drum testing"(Georgia Institute of Technology, 2023-09-21) Misch, Jacob ; Sprigle, StephenWheelchair users are highly susceptible to injury and immobility in the event of a wheelchair breakdown. Durability, or fatigue life, of manual wheelchair frames is currently evaluated using a standardized multi-drum test, which provides frequent impacts to the casters and rear wheels of the wheelchair. Not much is known about the underlying mechanics of the test, making it difficult to properly assess how appropriate this test is as a predictor of wheelchair frame longevity during real-world usage. This study aimed to investigate the applicability of the multi-drum test as an accelerated durability test by comparing breakdown statistics, vibrations, and shocks between the test and real-world usage. Triaxial accelerometers were used to measure the shocks and vibrations transmitted through an ultralightweight manual wheelchair frame during a portion of the multi-drum test. Occupant mass was varied (80 kg, 125 kg) to reflect standard user weight and maximum weight capacity of the chair. Root-mean-square acceleration and vibration dose values were greatest along the vertical axis, and overall similar for both occupant masses. Comparisons with existing literature suggest that the shocks and vibrations experienced within the multi-drum test far exceed values seen in real-world wheelchair usage. Similarly, frame-based fatigue failures are more common during the multi-drum test. These results suggest that the current test protocol is not well-suited to be an accelerated durability test for manual wheelchairs.
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ItemDataset for "Comparison of Propulsion Costs and Vibrations Across Carbon Fiber and Aluminum Rigid Manual Wheelchairs"(Georgia Institute of Technology, 2023-09-20) Misch, Jacob ; Allen, Taylor ; Suarez, Alicia ; Sprigle, StephenPropulsion efficiency and vibration exposure are two primary concerns when configuring a manual wheelchair. Recent manufacturing techniques have focused on using lightweight materials like carbon fiber to reduce energy expenditure during propulsion and improve vibration attenuation compared to aluminum or steel frames. This study utilized a robotic wheelchair propulsion device to measure the propulsion cost, vibration exposure at the seat, and vibration transmissibility through the frame during travel over smooth (tile) and textured (brick) surfaces for four rigid ultra-lightweight manual wheelchairs made of carbon fiber (N=1) and aluminum (N=3). Component selection (wheels, tires, casters, cushion) and the robotic occupant parameters (weight, fore-aft weight distribution, propulsion characteristics) were standardized across all four frames. Results show no meaningful differences between the carbon fiber and aluminum frames in any of the three variables (i.e., 95% CI does not fully exceed ±5% for propulsion cost or ±6% for vibration and transmissibility). These findings imply that other frame design features are more impactful to vibrations and propulsion efficiency than the material selection. Minimizing wheelchair vibration exposure and maximizing propulsion efficiency are more easily achieved through considerate selection of components, especially cushions and tires, respectively.
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ItemDataset for "Effect of wheels, casters and forks on vibration attenuation and propulsion cost of manual wheelchairs"(Georgia Institute of Technology, 2022-08-10) Misch, Jacob ; Liu, Yuanning ; Sprigle, StephenManual wheelchair users are exposed to whole-body vibrations as a direct result of using their wheelchair. Wheels, tires, and caster forks have been developed to reduce or attenuate the vibration that transmits through the frame and reaches the user. Five of these components with energy-absorbing characteristics were compared to standard pneumatic drive wheels and casters. This study used a robotic wheelchair propulsion system to repeatedly drive an ultra-lightweight wheelchair over four common indoor and outdoor surfaces: linoleum tile, decorative brick, poured concrete sidewalk, and expanded aluminum grates. Data from the propulsion system and a seat-mounted accelerometer were used to evaluate the energetic efficiency and vibration exposure of each configuration. Equivalence test results identified meaningful differences in both propulsion cost and seat vibration. LoopWheels and SoftWheels both increased propulsion costs by 12-16% over the default configuration without reducing vibration at the seat. Frog Legs suspension caster forks increased vibration exposure by 16-97% across all four surfaces. Softroll casters reduced vibration by 11% over metal grates. Wide pneumatic 'mountain' tires showed no difference from the default configuration. All vibration measurements were within acceptable ranges compared to health guidance standards. Out of the component options, softroll casters show the most promising results for ease of efficiency and effectiveness at reducing vibrations through the wheelchair frame and seat cushion. These results suggest some components with built-in suspension systems are ineffective at reducing vibration exposure beyond standard components, and often introduce mechanical inefficiencies that the user would have to overcome with every propulsion stroke.
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ItemDataset for "Propulsion cost changes of ultra-lightweight manual wheelchairs after one year of simulated use"(Georgia Institute of Technology, 2022) Misch, Jacob ; Sprigle, StephenManual wheelchairs are available with folding or rigid frames to meet the preferences and needs of individual users. Folding styles are commonly regarded as more portable and storable, whereas rigid frames are commonly regarded as more efficient for frequent daily use. To date, there are no studies directly comparing the performances of the frame types. Furthermore, while differences have been reported in the longevity of the frame types, no efforts have been made to relate this durability back to real-world performance of the frames. This study investigated the propulsion efficiencies of 4 folding and 2 rigid ultra-lightweight frames equipped with identical drive tires and casters. A robotic wheelchair tester was used to measure the propulsion costs of each chair over 2 surfaces: concrete and carpet. A motorized carousel was used to drive the chairs 511 km around a circular track to simulate one year of use for each wheelchair. After simulated use, 5 of the 6 wheelchairs showed no decrease in propulsion effort, indicating that the frames were able to withstand the stresses of simulated use without detrimental impact on performance. In the unused 'new' condition, rigid chairs were found to have superior (>5%) performance over folding frames on concrete and carpet, and in the 'worn' condition rigid chairs had superior performance over folding chairs on concrete, but were comparable on the carpeted surface.
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ItemModeling manual wheelchair propulsion cost during straight and curvilinear trajectories dataset(Georgia Institute of Technology, 2020-05-11) Misch, Jacob ; Huang, Morris ; Sprigle, StephenMinimizing the effort to propel a manual wheelchair is important to all users in order to optimize the efficiency of maneuvering throughout the day. Assessing the propulsion cost of wheelchairs as a mechanical system is a key aspect of understanding the influences of wheelchair design and configuration. The objective of this study was to model the relationships between inertial and energy-loss parameters to the mechanical propulsion cost across different wheelchair configurations during straight and curvilinear trajectories. Inertial parameters of an occupied wheelchair and energy loss parameters of drive wheels and casters were entered into regression models representing three different maneuvers. A wheelchair-propelling robot was used to measure propulsion cost. General linear models showed strong relationships (R2 > 0.84) between the system-level costs of propulsion and the selected predictor variables representing sources of energy loss and inertial influences. System energy loss parameters were significant predictors in all three maneuvers. Yaw inertia was also a significant predictor during zero-radius turns. The results indicate that simple energy loss measurements can predict system-level performance, and inertial influences are mostly overshadowed by the increased resistive losses caused by added mass, though weight distribution can mitigate some of this added cost. Videos of the test methods used to collect this dataset (wheelchair-propelling robot performing the three maneuvers, coast-down cart test for rolling resistance, and the scrub torque test rig) can be found here: http://hdl.handle.net/1853/60553